Fix type signatures for methods that return an IPromise
Remove unnecessary definitions and other small fixes

- Use optional parameters to delete unnecessary definitions.
- `queryParams` type is `any`, not `string`.
- Delete `getList` type definition without any arguments for `RestangularElement` since the documentation says that `subElement` is mandatory (https://github.com/mgonto/restangular#element-methods)
"users" is a RestangularCollection, `one` -> `all
Merge pull request #857 from santialbo/patch-5

restangular: Fix type signatures for methods that return an IPromise